Dennis Y. Loh

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SUMMARY Mice lacking p27(Kip1) have been created by gene targeting in embryonic stem cells. These mice are larger than the control animals, with thymus, pituitary, and adrenal glands and gonadal organs exhibiting striking enlargement. CDK2 activity is elevated about 10-fold in p27(-/-) thymocytes. Development of ovarian follicles seems to be impaired,(More)
SATB1 is expressed primarily in thymocytes and can act as a transcriptional repressor. SATB1 binds in vivo to the matrix attachment regions (MARs) of DNA, which are implicated in the loop domain organization of chromatin. The role of MAR-binding proteins in specific cell lineages is unknown. We generated SATB1-null mice to determine how SATB1 functions in(More)
In order to examine the mechanisms by which clonal deletion of autoreactive T cells occurs, a peptide antigen was used to induce deletion of antigen-reactive thymocytes in vivo. Mice transgenic for a T cell receptor (TCR) that reacts to this peptide contain thymocytes that progress from the immature to the mature phenotype. Intraperitoneal administration of(More)
During thymic development, T cells that can recognize foreign antigen in association with self major histocompatibility complex (MHC) are selected for survival (positive selection) and autoreactive T cells are eliminated (negative selection). Both of these selective events are mediated by interaction between the T-cell receptor (TCR) and the peptide-MHC(More)
The major problem in the study of T-cell development is that of tracking thymocytes of a given specificity. Recent studies have exploited natural correlations between the expression of a particular V beta gene segment and T-cell receptor (TCR) specificity. We and others (refs 5, 6 and M. Davis, personal communication) have taken an alternative approach. We(More)
Genomic Southern blots of DNA from eight strains of mice were examined for restriction fragment length polymorphisms in their loci encoding the variable region of the T-cell receptor beta chain (V beta), using 16 different V beta-specific probes. Mouse strains BALB/c, C57BL/6, C3H, and PL were identical, while strains SJL, C57BR, C57L, and SWR shared(More)
An adoptive transfer system was used to monitor physically the behavior of a trace population of TCR transgenic T cells in vivo. After subcutaneous injection of antigen in adjuvant, the antigen-specific cells accumulated first in the paracortical region of the draining lymph nodes, proliferated there for several days, and then moved into lymph node(More)
The cell-positional incidence of both spontaneous and damage-induced apoptosis of epithelial cells was assessed in longitudinal sections of the crypts of small intestine and colon of BDF1 mice. This was compared, using immunohistochemistry, with the pattern of expression of bcl-2, a suppressor of apoptosis. In the small intestine, apoptosis was maximal(More)
Clonal deletion provides an important mechanism for the elimination of autoreactive T cells. Deletion is accomplished by programmed cell death directed by interaction of the T-cell receptor (TCR) of the developing thymocyte with major histocompatibility complex elements in the thymic environment. In this report we present evidence to support the hypothesis(More)
The T-cell repertoire found in the periphery is thought to be shaped by two developmental events in the thymus that involve the antigen receptors of T lymphocytes. First, interactions between T cells and major histocompatibility complex (MHC) molecules select a T-cell repertoire skewed towards recognition of antigens in the context of self-MHC molecules. In(More)